Physical layer (PHY) data unit encoding for hybrid automatic repeat request (HARQ) transmission

Abstract

Hybrid automatic repeat request (HARQ) parameters for transmission of respective HARQ data units are determined. Determining HARQ parameters includes determining initial HARQ parameters, including an initial number of orthogonal frequency division multiplexing (OFDM) symbols that will be occupied by the HARQ data unit and an initial pre-coding padding factor corresponding to a boundary within a last OFDM symbol. Based at least in part on the initial pre-coding padding factor, it is determined whether the HARQ data unit will be misaligned with both a beginning of a first OFDM symbol occupied by the HARQ data unit and an end of a last OFDM symbol occupied by the HARQ data unit. When it is determined that the HARQ data unit will be misaligned, the initial pre-coding padding factor is adjusted to account for a reduced data tone OFDM symbol segment to be occupied by the HARQ data unit.

What is claimed is: 
     
       1. A method for hybrid automatic repeat request (HARQ) transmission in a wireless local area network (WLAN), the method comprising:
 generating, at a communication device, one or more HARQ data units to be transmitted according to an HARQ process; 
 for respective HARQ data units among the one or more HARQ data units, determining, by the communication device, HARQ parameters to be used for transmission of the HARQ data unit, including:
 determining initial HARQ parameters to be used for transmission of the HARQ data unit, including i) determining an initial number of orthogonal frequency division multiplexing (OFDM) symbols that will be occupied by the HARQ data unit and ii) determining, based on the initial number of OFDM symbols, an initial pre-forward error correction (pre-FEC) coding padding factor corresponding to adding padding bits prior to forward error correction (FEC) encoding of the HARQ data unit, 
 determining, based at least in part on the initial pre-FEC coding padding factor, whether the HARQ data unit will be misaligned an end of a last OFDM symbol occupied by the HARQ data unit, and 
 in response to determining that the HARQ data unit will be misaligned with the end of the last OFDM symbol occupied by the HARQ data unit, adjusting the initial pre-FEC coding padding factor to account for a reduced data tone OFDM symbol segment to be occupied by the HARQ data unit; 
 
 generating, at the communication device using the HARQ parameters, one or more HARQ aggregate data units to include the one or more HARQ data units; and 
 transmitting, with the communication device, the one or more HARQ aggregate data units to one or more other communication devices. 
 
     
     
       2. The method of  claim 1 , wherein generating the one or more HARQ data units comprises generating a plurality of variable length HARQ data units. 
     
     
       3. The method of  claim 2 , wherein determining HARQ parameters to be used for transmission of the one or more HARQ data units comprises determining respective HARQ parameters for respective ones of the plurality of variable length HARQ data units. 
     
     
       4. The method of  claim 1 , wherein generating the one or more HARQ data units comprises generating a plurality of fixed-length HARQ coding units. 
     
     
       5. The method of  claim 4 , wherein determining HARQ parameters to be used for transmission of the one or more HARQ data units comprises determining a set of HARQ parameters that apply to each fixed-length HARQ coding unit among the plurality of fixed-length HARQ coding units. 
     
     
       6. The method of  claim 1 , wherein determining initial HARQ parameters for transmission of the HARQ data unit includes selecting, based at least in part on the initial number of OFDM symbols, an initial segment boundary within a last-occurring OFDM symbol to be occupied by the HARQ data unit, such that, after encoding the HARQ data unit according to an FEC code, coded bits of the HARQ data unit end on the selected segment boundary. 
     
     
       7. The method of  claim 1 , wherein:
 the one or more HARQ data unit include at least one retransmission HARQ data unit, and 
 determining the initial number of OFDM symbols that will be occupied by the HARQ data unit includes determining the initial number of OFDM symbols that will be occupied by the retransmission HARQ data unit based on a number of coded bits that are to be retransmitted in the retransmission HARQ data unit. 
 
     
     
       8. The method of  claim 7 , wherein:
 the one or more HARQ data units further include at least one first transmission HARQ data unit, and 
 determining the initial number of OFDM symbols that will be occupied by the HARQ data unit includes determining the initial number of OFDM symbols that will be occupied by the first transmission HARQ data unit based on a number of data bits that are to be transmitted in the retransmission HARQ data unit. 
 
     
     
       9. The method of  claim 1 , wherein determining whether the HARQ data unit will be misaligned with the end of a last OFDM symbol occupied by the HARQ data unit comprises determining whether the HARQ data unit will be misaligned with the end of the last OFDM symbol occupied by the HARQ data unit further based on one or more pre-FEC coding padding factors determined for other HARQ data unit that are to be included in an aggregate HARQ data unit with the HARQ data unit. 
     
     
       10. The method of  claim 1 , wherein:
 the PHY data unit is a multi-user (MU) PHY data unit to be transmitted to a plurality of other communication devices, 
 the one or more HARQ data units include respective HARQ data units to be transmitted in respective aggregate HARQ data units to respective other communication devices among the plurality of other communication device, and 
 determining HARQ parameters to be used for transmission of the one or more HARQ data units includes determining HARQ parameters for a last-occurring HARQ data unit in each aggregate HARQ data unit such that the respective aggregate HARQ data units include equal numbers of OFDM symbols. 
 
     
     
       11. A communication device, comprising:
 a wireless network interface device implemented at least partially on one or more integrated circuit (IC) devices, wherein the one or more IC devices are configured to:
 generate one or more hybrid automatic repeat request (HARQ) data units to be transmitted according to an HARQ process, 
 for respective HARQ data units among the one or more HARQ data units,
 determine HARQ parameters to be used for transmission of the HARQ data unit, the one or more IC devices being configured to: 
 determine initial HARQ parameters to be used for transmission of the HARQ data unit, including i) determining an initial number of orthogonal frequency division multiplexing (OFDM) symbols that will be occupied by the HARQ data unit and ii) determining, based on the initial number of OFDM symbols, an initial pre-forward error correction (pre-FEC) padding factor corresponding to adding padding bits prior to FEC encoding of the HARQ data unit, 
 determine, based at least in part on the initial pre-FEC coding padding factor, whether the HARQ data unit will be misaligned with an end of a last OFDM symbol occupied by the HARQ data unit, and 
 in response to determining that the HARQ data unit will be misaligned with the end of the last OFDM symbol occupied by the HARQ data unit, adjust the initial pre-FEC coding padding factor to account for a reduced data tone OFDM symbol segment to be occupied by the HARQ data unit; 
 
 
 wherein the one or more IC devices are further configured to:
 generate, using the HARQ parameters, one or more HARQ aggregate data units to include the one or more HARQ data units, and 
 control the wireless network interface device to transmit the one or more HARQ aggregate data units to one or more other communication devices. 
 
 
     
     
       12. The communication device of  claim 11 , wherein the one or more IC devices are configured to generate the one or more HARQ data units at least by generating a plurality of variable-length HARQ data units. 
     
     
       13. The communication device of  claim 12 , wherein the one or more IC devices are configured to determine respective HARQ parameters for respective ones of the plurality of variable length HARQ data units. 
     
     
       14. The communication device of  claim 11 , wherein the one or more IC devices are configured to generate the one or more HARQ data units at least by generating a plurality of fixed-length HARQ coding units. 
     
     
       15. The communication device of  claim 14 , wherein the one or more IC devices are configured to determine a set of HARQ parameters that apply to each fixed-length HARQ coding unit among the plurality of fixed-length HARQ coding units. 
     
     
       16. The communication device of  claim 11 , wherein the one or more IC devices are configured to select, based at least in part on the initial number of OFDM symbols, an initial segment boundary within a last-occurring OFDM symbol to be occupied by the HARQ data unit, such that, after encoding the HARQ data unit according to an FEC code, coded bits of the HARQ data unit end on the selected segment boundary. 
     
     
       17. The communication device of  claim 11 , wherein:
 the one or more HARQ data unit include at least one retransmission HARQ data unit, and 
 the one or more IC devices are configured to determine the initial number of OFDM symbols that will be occupied by the retransmission HARQ data unit based on a number of coded bits that are to be retransmitted in the retransmission HARQ data unit. 
 
     
     
       18. The communication device of  claim 11 , wherein:
 the one or more HARQ data units further include at least one first transmission HARQ data unit, and 
 the one or more IC devices are configured to determine the initial number of OFDM symbols that will be occupied by the first transmission HARQ data unit based on a number of data bits that are to be transmitted in the retransmission HARQ data unit. 
 
     
     
       19. The communication device of  claim 11 , wherein the one or more IC devices are configured to determine whether the HARQ data unit will be misaligned with the end of the last OFDM symbol occupied by the HARQ data unit further based on one or more pre-FEC coding padding factors determined for other HARQ data unit that are to be included in an aggregate HARQ data unit with the HARQ data unit. 
     
     
       20. The communication device of  claim 11 , wherein:
 the PHY data unit is a multi-user (MU) PHY data unit to be transmitted to a plurality of other communication devices, 
 the one or more HARQ data units include respective HARQ data units to be transmitted in respective aggregate HARQ data units to respective other communication devices among the plurality of other communication device, and 
 the one or more IC devices are configured to determine HARQ parameters for a last-occurring HARQ data unit in each aggregate HARQ data unit such that the respective aggregate HARQ data units include equal numbers of OFDM symbols. 
 
     
     
       21. The communication device of  claim 11 , wherein:
 the wireless network interface device comprises one or more transceivers, and 
 the one or more IC devices are configured to control the one or more transceivers to transmit the one or more HARQ aggregate data units to one or more other communication devices. 
 
     
     
       22. The communication device of  claim 21 , further comprising:
 one or more antennas coupled to the one or more transceivers.